Ok so I'm on nexplanon I've been on since 4weeks postpartum && my baby is about to be 4month on the 29th ... Me & my…

Ok so I'm on nexplanon I've been on since 4weeks postpartum && my baby is about to be 4month on the 29th ... Me & my boyfriend has sex before my 6week check up lol :( Buh at my 6week check up I was fine not prego or nun lol Buh now I feel like a pulse around my lower stomach I keep thinking I'm pregnant because it use to happen w. My daughter lol help what is it? Oh I also took a test it came out negative .